text:
Where can I take my ultralight aircraft?
I know many airports do not allow ultralight aircraft but can I take it to work, home, or to the bar? What is the limits of freedoms of travel in an ultralight?

Possible duplicate of What regulations are in place for ultralight vehicles flying over US national parks?

I don't think the picture you posted fits the definition of an ultralight in the United States.

https://en.wikipedia.org/wiki/Workhorse_SureFly  "The 70 mph (110 km/h) hybrid electric has a 200-hp gasoline generator giving up to 70 mi (110 km) range over 1 hour. It has four propeller arms, each with two electric contra-rotating propellers powered by a gas turbine or piston engine generator along a battery pack. Targeting a price of $200,000, it can lift a 400 lb (180 kg) payload and include a ballistic parachute.
The SureFly would operate as a conventional helicopter, like the similarly priced two-seat Robinson R22, but would be easier to fly and safer with its integral parachute. "

Taken from a more specific answer by @Pondlife to a question about ultralights and National Parks:

For ultralights specifically, the regulations are in 14 CFR 103 which has only a few very simple restrictions on where ultralights can operate. 103.15 says you can't operate over a congested area or a crowd of people and other restrictions are the obvious ones: don't fly near airports without ATC approval, don't enter restricted airspace, and do follow NOTAMs.

I understand you were giving a basic-level answer but actually for MOST airports without control towers there is no need to get ATC approval before flying an ultralight there.


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Is it Ok for co-pilots to snooze?
What are the policies on long flights and taking shifts sleeping between 2 pilots?
Could a pilot set the cruise control and alarm during any flight?

I heard a crazy story of a pilot flying freight in a piston twin who would set an alarm clark and nap on autopilot, no one else in the plane.  Probably back in the 1980's.  Once he scraped something on the ground but survived, according to his friend who told me the story.

I can tell you that on very long flights, three pilots may be booked. As far as I am aware, all are available during critical phases of flight (takeoff, landing) but otherwise they rotate and have off time for rest.

@quiet_flyer I heard a similar story only one day he had an unexpectedly strong tailwind and hit a mountain.

Yes, it is called in-seat-rest.

This is the process whereby pilots may take short periods of sleep (naps), while temporarily relieved of operational duties in accordance with carefully prescribed ‘controlled rest’ procedures, when part of a two-man operating crew of an in-flight aeroplane.

Source: skybrary

The question was tagged "FAA". This answer applies to certain areas outside of FAA jurisdiction. The FAA is largely silent on this issue.

That is a really interesting skybrary article you linked to; I'd suggest editing the answer to the effect of  "you  can find much more information here" or something.

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text:
Is GOCE a satellite or aircraft?
This vessel (GOCE) is in orbit and maneuvers by using air similar to a plane to create lift and turn. The solar powered ion thrusters powers it continuously inside the atmosphere for years. Is this technically a plane, satellite, or a missile?

Source: https://space.stackexchange.com/a/33202/18879

I took the liberty of editing out the off-topic side question (not only because it's off-topic but also because you should only have one question per post). Feel free to roll back if you disagree.

By definition it's a spacecraft instead of an aircraft, because it relies on orbital velocity to stay up, not air in any form. It's a low drag satellite.

A satellite is an object in orbit. A satellite keeps a constant altitude if it is traveling at the correct orbital speed for their altitude. Otherwise it will be in an elliptical orbit where the altitude is constantly changing. In any case, satellites are (almost) in free-fall
An airplane travels at much, much lower speed than orbital speed. Airplanes keep their altitude because their wings produce lift.
Satellites in lower orbited are subject to atmospheric drag, albeit to much smaller extentd than planes. GOCE was orbiting Earth at an - for satellites - very low altitude (224 km). There is hardly any atmosphere at this altitude, but at an orbital velocity of 7.8 m/s (51337 kts), atmospheric drag is still a problem.
Therefore the structure of GOCE was particularly designed for low drag. The wings were flat without camber. They did not produce any lift. GOCE used ion thrusters to compensate the atmospheric drag and maintain orbital velocity.

Photo: ESA

Photo: ESA
Missiles are self-propelled guided weapons. I can assure you that GOCE was not a weapon.
[TL;DR]: GOCE was a satellite, because it orbited an astronomical body. It was not a plane, because its wings did not produce lift.
GOCE´s 20 month mission ended on November 11, 2013 with the planned destructive re-enty into the atmosphere. It measured Earth´s gravity field and acquired a precise model of the Earth geoid:

Image: ESA

"The wings were flat without camber. They did not produce any lift." - What were the wings for, then? I would have thought that if a surface doesn't produce lift, then that surface is not considered a wing.

@TannerSwett, They provide area for solar panels, and they stabilize the space craft. Indeed, it would be more correct to call them fins instead of wings

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text:
Do planes depreciate like cars?
Let's say I was in the market for buying a Cessna. What benefits would buying a new Cessna have over an older one? With cars, the resale value does hit a floor as long as it is safe to drive. Are planes the same? Is the fuel efficiency worth buying a new Cessna or is it more of a status thing?

New ones weigh more and are starting to have proprietary or otherwise hard-to-modify avionics.  That said, if you have a business that has a need for and can support a plane you may be able to take advantage of some tax benefits.

Do planes depreciate like cars?

Planes do not really depreciate like cars per say but aircraft engines kind of do!
Planes are a bit different than cars due to the certification process being far more verbose. Year to year changes tend to be non-existent or come down to trim/paint options. As such a well maintained old aircraft with a fresh/low time engine may fetch more than a new aircraft with a run out engine.
There are also a lot more factors that go into the value of an aircraft even from airframe to airframe in the same make and model where cars can have some options the avionics combinations for most light aircraft are nearly endless.

Is the fuel efficiency worth buying a new Cessna or is it more of a status thing?

A brand new Cessna 172 is no more fuel efficient than a 172 from 30 years ago (more or less) because the design largely has not changed. Unlike cars that get small aerodynamic and engine changes often, it's far more complicated to change aircraft designs and deal with the certification so designs remain largely unchanged short of small and limited improvements.
I'm not really sure its a status thing, thats highly opinionated and a bit off topic here.


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Which modern passenger aircraft has the simplest, most automated systems?
I'm looking for an aircraft meeting the following criteria:

Manned (no drones, etc.)
Has or had a production run (no prototypes, design-only, etc.)
Capable of carrying multiple passengers who are not crew-members (no single-seaters or 2-seaters where both people are required to be part of the crew)
Modern avionics, either designed that way or significantly retrofitted if older base model
Has the fewest configurable knobs/switches/buttons/etc. in the cockpit that are related to the main flight systems like the engines, APU, electrical system, hydraulic system, control surfaces, brakes, etc. Note that computerized touchscreen displays that expose complex configuration of these systems should be counted against the aircraft's complexity, unless the computer automates the configuration of the system by default. Ignore cosmetic things like knobs to let you change the brightness of the lighting; and don't count the FMS, or displays or indicators that give the pilots information about the flight status, either.

Answers don't have to point out THE absolute best craft fitting these criteria currently available; if you have broad experience with systems complexity in a lot of modern aircraft, and you can think of one off the top of your head that is especially clean and simple compared to the rest (either due to automation or just fewer systems to deal with), point it out in an answer.
Bonus if you can explain what is automated or taken care of for the pilot without them having to worry about it under normal conditions, but if you're going to explain this, only focus on automation that is unusual or new or unique to the aircraft, not things that are automated on most/all current aircraft.
Here's the question stated in another way: To take an aircraft from cold and dark, into the air and land it again in normal, uneventful conditions, which aircraft meeting the criteria above can accomplish this with a minimum of input from the pilot?

Piper Cub

A hot air balloon. This seems to me like a very subjective, opinion-based question that will almost certainly lead to discussion. That doesn't mean it's a bad or uninteresting question, but it does mean that it may not be a good fit on this site.

Maybe if you said why you're asking it might help. Are you actually looking to buy an aircraft, creating a sim, writing a story?

You don't mention if fictional a/c count: apparently the Tie Fighters in the new SW movie seem to take very little time from cold&dark to flight. I'm sure a lot of stuff is automated in there

Simple and automated are generally oxymorons when it comes to aircraft systems. Simplest aircraft will not have the modern avionics you ask for.

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Are all student pilots required to have a TSA background check or just non-US Citizens?
I know that non-US Citizens have to go through approval with the TSA before beginning flight training, however could one avoid that fee by waiting until after getting Citizenship to start flight training?
I am a Resident Alien and currently considering starting flight school, I'm just wondering if waiting until I apply for Citizenship in 2021 is worth doing or if I could start now.
My fear is that I am already 30 and would like to eventually get a position as a Part 135 pilot. I am worried that I am already too old to be making such a change and thus adding time would just be making the situation more hopeless than it may already be.

This page on the FAA website has details on getting your student pilot certificate.

• Resident and US citizen student pilots follow Student Pilot’s
Certificate Requirements.
• Foreign student pilots (non-resident) follow the Alien Flight Student Program

It appears from your question that you should follow the same procedure as US citizens.
Refer to AC 61-141. Everyone must get a TSA screening before being issued a Student Pilot Certificate.

6.3 The Flight Instructor Verifies the Applicant’s Government-Issued Photo ID.
The flight instructor verifies the applicant’s identity and
enters information from the applicant’s ID. If the applicant cannot
present acceptable ID, discontinue the application process. Verify
that the applicant has entered a correct date of birth. IACRA will not
process an application unless the applicant is within 90 calendar-days
of his or her 14th birthday or older. If the applicant is not of
sufficient age, discontinue the application.
7.8 TSA Security Vetting and Temporary Certificate Availability of the Paper Method.
Provided the applicant is not deemed a security
risk and is at least 14 years of age, the Airmen Certification Branch
issues a permanent Student Pilot Certificate and mails it to the
applicant. Applicants must also wait to receive a permanent plastic
certificate in the mail.

What led to question is that the AFSP program linked to in the above document states "Who must participate in the Alien Flight Student Program? Persons seeking flight training must submit a request if they are not citizens or nationals of the U.S." and being a resident alien I am neither a National nor a US Citizen. However, this does answer the question that everyone has to go through the TSA check.


text:
Is there a forced retirement age for Part 135 pilots?
I know that international Part 135 operations have a set retirement age of 65, however if one was to stay within FAA jurisdiction is there a set retirement age for Part 135 operations?

There is no FAA mandated retirement age for part 135 operations, although there was in 2017, a proposal in Congress that would limit the maximum age but only for certain operators. As of the date of this answer there is no regulation for 135 pilot ages.
It's up to the operator then to decide if they want to hire somebody who can only fly domestic routes. For some this may not be an issue, for others it may be a deal breaker.


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What would be logged as the destination for an emergency landing in a field?
When logging flights you have a departure point and an arrival point, how would you log the arrival point if you were to have to perform an emergency off field landing in a field or on an interstate?

I'd say lat/long, but that's only a guess.

However you want.

I would just write "off fld" in the destination box, if there is one, and describe the location in Remarks.  "Emerg ldng on I-90 2 mi S of Whereverville"  or "Pracaut lndg field 2 mi W of Middleofnowheretown".
You aren't going to get audited over that kind of stuff so don't worry about hyper precision.  If anybody ever looks at your logbook it's just going to be to validate flying times for the purpose of a license or rating.  The other stuff is mostly for your own historical record.

Yes.  And I have made frequent (non-emergency) landings on dry lakes and such, logged as just "XX lake" or similar.


text:
Are ATC assigned altitudes temperature compensated?
For the purposes of commercial air traffic operating in a terminal/approach space area that has temperature compensation applied to waypoints in the active flight plan, if ATC assigns an altitude, will the assigned altitude be a temperature compensated altitude?
If so, how does ATC know what factor to apply to the procedural altitude?
If not, then an ATC assigned altitude (non-compensated) could be interspersed with compensated altitudes and possibly cause non-monotonic descent or ascent.

Related: Who does have a responsibility to make altitude correction for cold temperature?

Answering for the US. Controllers in the US do not assign altitudes differently based on temperature.
From the AIM:

5−1−17. Cold Temperature Operations Pilots should begin planning for
operating into airports with cold temperatures during the preflight
planning phase. Instrument approach charts will contain a snowflake
symbol and a temperature when cold temperature correction must be
applied. Pilots operating into airports requiring cold temperature
corrections should request the lowest forecast temperature at the
airport for departure and arrival times. If the temperature is
forecast to be at or below any published cold temperature restriction,
calculate an altitude correction for the appropriate segment(s) and/or
review procedures for operating automatic cold temperature
compensating systems, as applicable. The pilot is responsible to
calculate and apply the corrections to the affected segment(s) when
the actual reported temperature is at or below any published cold
temperature restriction, or pilots with automatic cold temperature
compensating systems must ensure the system is on and operating on
each designated segment. Advise ATC when intending to apply cold
temperature correction and of the amount of correction required on
initial contact (or as soon as possible) for the intermediate segment
and/or the published missed approach. This information is required for
ATC to provide aircraft appropriate vertical separation between known
traffic.

All pilots in the same general area of airspace are issued a common altimeter setting, which ensures everyone is on the same reference point of pressure as it relates to the weather, but not the temperature, specifically. ATC separates using altitude or lateral primarily and has a separation standard for this reason, so that if someone is off by a few hundred feet, it doesn't cause a collision due to being off as a result of atmospheric conditions. If nobody is correcting their altitude and basing it off ATC assignments and a common altimeter, there really shouldn't be much deviation.
Source: former ATC'er.

The only examples of temperature affecting altitude assignments that I've seen are on approach plates, where certain procedures change, or may not be usable at very low temperatures. I thought they were pretty weird, when I first saw them, and I'm a (retired) Colorado controller! :)


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What are the bulges (with what look like air intakes) on the lower fuselage of the An-22?
On both side of the lower fuselage of the AN-22 there are long bulges.  While the undercarriage doors are visible, they only account for a small proportion of the length, making me doubt they're just fairings.  There are also what look like air intakes though no obvious outlets on the photo below or other photos at
Wikpiedia, but the video there might show something on the starboard bulge, forward of the undercarriage.
The cross section and (poorly-translated) text at globalsecurity.org don't say much, except to hint that they're outside the pressurised hull.  A human-scale hatch/door just forward of the undercarriage doors suggests they're not fuel tanks.
So what are they?

An-22 photo by user Toshi Aoki from Wikimedia Commons

This cutaway drawing shows it's the airconditioning unit, which would also explain why it has an air intake.

Source - ww2aircraft.net
Zoomed version:

The relevant part of the legend:

Next to the air conditioning unit, the sponsons also house other parts (as pointed out by @sophit in the comments):

142: Port entry door
141: port entry tunnel and inner pressure door
140: Triple twin-wheel main undercarriage bogies
135: Sponson mounted cargo winch, port & starboard
138: Hydraulic retraction jacks
136: Inward opening mainwheel bay doors
112: Spons bag-type fuel tanks
111: Avionics racks, port and starboard
110: Fuselage sponson tail fairing

A rare immediate acceptance from me - normally I leave it 24 hours but I didn't see much point.  I'm surprised that you found anything useful on pinterest

I think I need to review the answer, this a AN-12, not an AN-22. But I think the answer will be same. Let me see if I can find an AN-22 cutaway

Strange, I get pinterest hits but they're not relevant (even with quotes) for the same search.  Maybe Google knows I get frustrated with pinterest on the rare occasions I click  link to it and suppresses the results

@ChrisH, you'll be happy to learn I found the correct AN-22 cutaway drawing outside of Pinterest :)

Note that there's something more than the air-conditioning: the entry door and tunnel (141 and 142), some fuel tank (112) and some avionics (111)! This is a really nice example of the efficient use of space which is of paramount importance in the aerospace world

@sophit, good catch, I mainly focused on the front part as that question was related to the inlet. I'll include the other parts too.

@sophit, I think it's more a case of "we're already taking a drag penalty for the wheel fairings, so let's elongate them and pack a bunch more things in".

@Mark:  "to-may-to to-mah-to"


text:
Is it legal to land aircraft in national parks and state forests in Australia?
I was reading about the (very) short takeoff and landing capabilities of the SuperSTOL light aircraft and it occurred to me that it would be pretty easy to set down in a national park or other remote area so long as there was a reasonably flat clearing and visibility.
But what are the regulations regarding legally landing in such places?

The answer to your question, is yes and no.
CAR 92 (1) states that:

An aircraft shall not land at, or take-off from, any place unless: ... (d) the place... is suitable for use as an aerodrome for the purposes of the landing and taking-off of an aircraft; and, having regard to all the circumstances of the proposed landing or take-off (including the prevailing weather conditions), the aircraft can land at, or take-off from, the place in safety.

As you can see, you are able to takeoff and land away from a proper aerodrome provided it is safe to do so. As you can see here, misjuding this level of safety can be fatal.
The Civil Aviation Advisory Publication (CAAP) 92-1(1) provides guidelines on what constitutes a safe landing/takeoff field other than an aerodrome. These safe areas are known as Aeroplane Landing Areas. Although the CAAP is only a guide, it is highly recommended that any area you choose to operate from meets these minimum standards.
So you are allowed to takeoff and land outside of an actual aerodrome. But your question includes national parks. The rules surrounding these are outside of my knowledge (and they vary from state to state) , but I do know that many parks carry restrictions on vehicle entry, and the types of activities permitted. I would therefore find it very surprising if you received permission to land a plane in their park (if you found a safe landing site in the first instance).
EDIT: Some commercial flying is permitted within national parks. For instance, they use helicopters and a person on a sling rope to collect crocodile eggs in Kakadu. Obviously then some activities can be approved in a national park. I'd say it all depends on the specific park and the activity being performed. Private flying away from an aerodrome? You would have to check. In any case, my answer to your question is you can land out bush somewhere but possibly not in a national park.

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text:
Why simple paper planes fly better than most "realistic" paper plane models?
Just a A4 paper sheet folded into a plane seems to fly decently. But a model of actual (big) plane made out of paper is only good at falling...
What is different for paper planes? Are there "modern and improved" designs of paper planes?

do you have pics of the ones you compared? often paper planes have a very thin hull and wings while model aircraft have much thicker hull and wings, often heavier as well

Something like if one tries a Google Image Search of "paper plane model".

I suspect the answer will have something to do with Reynolds numbers. When you scale down your 747 to A4 size, you are not scaling down the viscosity of the fluid in which the object flies.

The article also mentions them.

The reason is really the size! Air molecules have the same size if they flow around a small paper airplane or a big real airplane, but since their relative size is so much smaller when they flow around the real airplane, friction effects are much smaller for the big airplane. When comparing airplanes of different sizes, a dimensionless number first formulated by Osborne Reynolds is most helpful. It is basically the ratio of inertial to viscous forces in the airflow, and the formula is
$$Re = \frac{l \cdot v}{\nu}$$
Nomenclature:
$Re\:\:\:$ Reynolds number
$l\:\:\:\:\:\:$ characteristic length, for example wing chord
$v\:\:\:\:\:$ airspeed
$\nu\:\:\:\:\:$ kinematic viscosity of air
Flows with the same Reynolds number behave identically, but your scaled-down aircraft flies at a very different Reynolds number than the original (both speed and characteristic length are a lot lower), so the airflow around it will be very different. For it, the air looks more like a syrup when that around the original is like flowing water! Therefore, lift creation needs different means at this scale (wings with more chord, for example), and the paper airplane is better suited to cope with this particular flow condition.
The next difference is wing loading: The paper airplane is very light; its mass per area is low. Therefore, it can fly at a slower speed than your scaled-down real airplane, and it will be easier for you to launch the paper airplane properly into the air. The scaled-down airplane needs to be thrown harder, but still straight, and this might be another reason for it falling down quickly.

How will a giant paper (or other material if paper is too weak) plane fly? Will it also sink like a stone?

With a bit of cheating, it can be made to work. Look at cardboard, which is essentially glued paper. Smart construction can reinforce paper to be strong enough. You should be able to pull off a 2 meter glider.

@Anonymous: Increasing size will help, even if the shape of the plane stays identical. But you definitely need something stronger than paper. The plane will fly, but will need more thrust (if engines are installed) or fly less far when launched compared to a plane with conventional shape due to its lower aerodynamic efficiency.

@MSalters: A 2 meter glider is essentially a model aircraft, and they can be made similar to the real ones. But optimization for this scale will still lead to bigger and stubbier wings and airfoils with less camber and thickness, for example.

and at the 2 meter scale you will be using fiberglass or if you have deep pockets carbon

@PeterKämpf So the ratio of the sizes for paper-plane:air-molecule to real-airplane:air-molecule is very different? In my reasoning, the air molecule is much much smaller than either of them, that the difference in size of the paper-plane to the real airplane is negligible.

@midnightBlue: What counts is not the size of the airplane but the thickness of the boundary layer, the layer of air where flow speed drops from the free flow value to zero at the surface of the wing. Using the chord length as a proxy for boundary layer thickness is a trick to make measurements easier.


text:
What's the purpose of "over G" penalties in Red Bull Air Race?
This post mentions that if a Red Bull Air Race pilot exceeds 10G acceleration limit for longer than 0.6s on their plane then they are unconditionally disqualified with "did not finish" result no matter how they perform otherwise.
What's the purpose of this restriction? Is this to prevent the airplane from falling apart or pilot getting unconscious during the (low altitude) race?

This is not unprecedented in racing.  In WRC Rally car racing, if there are race stages that allow speeds of greater than 130km/h, that stage can be canceled for safety reasons.  Stock car racing requires governors on the engines to effectively cap horsepower and therefore speed.

Probably more important than protecting the pilot, it protects spectators from an unconscious pilot's plane wondering into a crowd i.e the 2011 P51 Reno Air Race crash.

@JPhi1618: To add on your comment (I remembered WRC broadcasts showing onboards where the speed is > 200 kph so tried to look this up): I think in WRC, it's about average speed and it's not written in stone. In NASCAR, there are restrictor plate races where plates are installed which put a hard, physical cap on engine power (leading to, IMHO, knowing my opinion is often strange :D) really great races with all cars cramped together, leading to a test of one's nerves and psyche.

It's a safety rule to protect the limits of the airframe and the pilot.
See the video (also on youtube) from this Red Bull Air Race page which explains the rules. The G-limit is discussed from 3:30.
The following is a quote from the relevant section of the video.

Maximum load factor, that is how much G's is the pilot pulling. That has
  issues [...] the structure of the
  airplane is designed to withstand a certain amount of G. We need to
  ascertain, to check, that the pilot isn't exceeding that amount of G,
  so we monitor that very carefully. A thousand times a second we're
  monitoring the G inputs that the pilot is putting on the airplane. So
  if you exceed the maximum G's then DNF (Did Not Finish)

It's a sensible rule IMO, otherwise pilots will be tempted to push themselves and their airplanes just a little harder each time, and someone would eventually get killed.

@GdD Or, perhaps just as badly, people would lose solely because they were unwilling to gamble with their life. Without the rule, the competition could become closer to Russian roulette than any real show of skill (in theory, anyway).

It can be safety limits as discussed above or for operational prudence.  One other possibility is to place limitations on the types of maneuvers which could be performed for strategy reasons ie  limits to the radius of turns or vertical maneuvers for added challenge in energy management.


text:
Why would a plane descend rapidly in uncontrolled manner after a steep turn?
Here's some footage from 2010 Red Bull Air Race.  At 0:17 the plane is passing through a gate and then makes a steep turn to the left and that requires the plane to have left wing pointing almost downwards and right wing pointing almost upwards - this is how such turns are typically done. Right after the turn ends - at about 0:18 - the plane just starts falling down. It's only the pilot's skill which prevents it from entering water with left wing pointing down - the pilot promptly levels the airplane such that wings are now horizontal and this mostly stops the incident from developing.
How is this turn different from "good" turns which don't end up with plane falling down?

It's probably pilot error that caused the drop.

Maybe, but what did he do wrong?

@GdD and the pilot discusses and describes it later in the video

@Federico I hardly understand his explanation. He says "he believes" he left the gate with too great an angle. I don't have enough knowledge to understand how this error explains the behavior of the plane which followed.

The pilot explains in the video that the cause was a "G stall' or accelerated stall due pulling too hard which was aggravated by poor initial setup. This caused a momentary degredation of lift and control. Is your question asking for an explanation of his statement of the cause, or are you asking for An alternative explanation?

Markus Voelter interviewed Matt Hall for an episode of his omega tau podcast. They discuss this incident in more detail at 1:13:00.
The aircraft experienced a high speed g stall, also called an accelerated stall. Stall is determined by the angle of attack, which is the angle of the airflow hitting the wing. Stall is most often thought of at low speed, because as the plane goes slower, it takes higher angle of attack to provide enough lift, until it reaches the stall angle of attack and stalls. But this can also happen at high speeds in an aircraft performing a high g turn. Much higher lift is required to make the airplane turn, meaning much higher angle of attack is needed. Trying to turn the aircraft too tightly can increase the angle of attack too far, and the airplane stalls at a high speed.
The other factor is that the airplane will tend to roll left due to torque from the engine and P-factor of the propeller. Since the plane was already in a left hand turn, this plus the stall made the airplane roll past 90 degrees and head down towards the water.
Another aggravating factor was the airplane's stability, which is discussed at 1:31:00. The CG was fairly aft, making the plane less stable. The elevators were also over-balanced, meaning they would tend to make the airplane pitch up even further as the airplane pulled more g's. These changes had helped to make the plane a bit faster but were corrected after the incident to make it safer.
On the human factors side, Matt also mentions that he had a head cold at the time, and made the decision to take a phone call right before his flight, meaning he was distracted and not at his best.
Elsewhere in the interview he mentions that when he flies in air shows, he is more conservative in his margin of safety than other pilots might be.

You don't need the money if you're dead. So it's just a show.

I haven't watched the video, but keep in mind that to a first order approximation, lift is perpendicular to the airfoil.
In ordinary level flight or close to it, this causes the lift vector to have a significant vertical upwards component, which nicely offsets the force of gravity acting downwards on the aircraft's weight.
However, if the airfoil (in this case, wings) are fully vertical, then the lift generated by that airfoil becomes fully horizontal. The wings don't care about their angle to the ground; only about the movement through the surrounding air.
However, gravity still applies that same vertical force downwards.
Level flight (in any attitude) requires that there is a upwards vertical component to the lift vector, and that this component is the same as the downwards vertical force of gravity. If the two are unequal, the aircraft will climb or, in this case, descend.
With gravity still pulling the aircraft down, and lift acting horizontally (sideways), there is nothing left to maintain the aircraft's altitude, and the aircraft will do the proverbial drop from the sky. To recover you'd better hope you're able to level the aircraft at least somewhat, to get a bit of vertical lift out of the wings.
This, too, is why if we don't apply additional upwards lift in a turn, we'll lose altitude; the lift vector has a smaller vertical component (even though the absolute value of the lift vector is unchanged), but gravity doesn't relent, so gravity wins until we reestablish a balance between gravity and lift, typically by raising the nose a little.

+1 It also does not help that these racers have almost  flat wings, that is very little dihedral angle.. In a regular aircraft each wing produces a different lift vector in a turn, with a flat wing it's all in one direction and much more sensitive to pilot inputs.

What this comes down to is that generally, wings create lift in whatever direction the top surface is facing.
In normal flight, most of the force holding the airplane up is upward lift from the wings. When a plane is level, all of the lift force from the wings is directed straight up, and so the plane is able to maintain altitude. Even in an ordinary (non-aerobatic) banked turn, the tops of the wings are still facing mostly up, so the pilot can maintain altitude by just increasing the angle of attack a bit.
In this video, the turn the pilot made was no ordinary banked turn. It looks like he banked the plane by about 90 degrees. At a 90 degree bank angle, all of the lift from the wings is pointing sideways (into the turn), and none of it is holding the plane up. So unless there's something else holding the plane up, that plane is going to start falling.
There are two ways to keep from falling in an extreme banked turn. One is to keep the turn brief, so that you don't fall very much. The other is to stay up using thrust and fuselage lift, as detailed in the answers to this question: Can you fly an airplane at a 90° roll angle without losing altitude?

What he does is called a "G stall". Basically, he he pulled the aircraft into a harder turn (which is what he describes about 0:57 in the video). What that did was increase the centripetal force on the aircraft (measures in terms of Earth gravity, or "Gs"). This acrobatic pilot describes the effect

The stall speed of an aircraft increases as the wing loading increases. To be precise the stall speed increases with the square root of loading so if an aircraft stalls at, say, 60mph in 1G level flight in a particular configuration it'll stall at 120mph at 4G, 180mph at 9G etc. (This is one reason why "stall speed" can be a misleading term - a wing stalls at a given angle of attack.)

This is also sometimes called an accelerated stall, which can be quite common in these types of events, due to the rapid inputs and stresses the pilots are putting on the aircraft

Accelerated stalls are often caused by abrupt or excessive control inputs made during steep turns or pull-ups. If you’re in a dive and pull back with enough suddenness and force to load the airplane to a typical design load factor of 3.8 G’s, you’ll enter an accelerated stall if the airspeed drops below 1.95 times the stall speed at 1 G loading (the square root of 3.8 is approximately 1.95).

It then describes the crash of Midwest Express Airlines Flight 105, which offers the following illustration (source)

What happened was an accelerated stall "snap roll", which Matt Hall explains at 50 seconds into the video, he "g stalled" the plane "which rolled me slightly past the knife edge", so the plane was literally slightly upside down turning downwards towards the water, as opposed to falling.
An accelerated stall snap roll occurs in high g turns when one wing experiences a high speed stall before or more than the other. The plane rolls towards the stalled wing increasing it's angle of attack further still, while reducing the angle of attack on the other wing, making the situation worse. Note that an accelerated stall snap roll only requires excessive elevator at high speed, no aileron or rudder inputs are required.
In this case, the pilot quickly eased off the elevator input, which stopped the stall and allowed the ailerons to function to recover from the snap roll.
This was somewhat unlucky, as the snap roll could have rolled the other way, so the plane would have been turning upwards away from the water instead of downwards into the water. It's pretty much a 50% - %50% chance which which direction a plane will roll in a snap roll, unless ailerons are used to initiate the roll before applying excessive elevator.
True elevator only snap rolls are done on model aerobatic airplanes, either on purpose as an aerobatic maneuver, or unintended in the case of model pylon racing, which is the same circumstance as Matt's incident (without the risk to the model pilots life). I've even done this on a small radio control glider in a vertical dive (required to maintain speed since drag is high in a snap roll). Pull too far back on the transmitters elevator control and the glider just rolled, without a hint of upwards pitch. Eased off the elevator and the model recovered from the snap roll and responded to non-excessive elevator inputs in a normal fashion.

The pilot claims that the cause of the left roll was torque.  As always, pilots can be wrong, but Matt Hall has a lot of experience in departures from controlled flight.

@WayneConrad - At 50 seconds into the video, Matt Hall stated he "g stalled" the plane "which rolled me slightly past the knife edge", which is a description of a snap roll, a roll due to stalling (one wing before or more than the other).  A snap roll is one way that a rolling torque can be produced,  and can be more severe than what is possible with ailerons. In this case, the snap roll wasn't severe, and Matt quickly recovered. Calling it a torque doesn't conflict that the cause of that torque was a snap roll.

In the interview linked to by foot, Mr. Hall specifically blames engine/prop torque.  That's what I recall, but I could be remembering it wrong.

@WayneConrad - the OP includes a link to the video: some footage from 2010 Red Bull Air Race. Matt's explanation starts around 50 seconds into the video. No where in that video does Matt mention prop torque, and prop torque is an issue at low speed, mostly on takeoffs, and would be unrelated to "g stalling" the plane as Matt explains.

@WayneConrad - here's a video of an accelerated stall snap roll. Left aileron input is used initiate the roll (otherwise snap roll direction would be random), then at 14 seconds into the video, excessive elevator input is used to visibly pitch the nose upwards and create an accelerated stall snap roll .  An accelerated stall snap roll can be a much faster roll than what is possible just using ailerons.


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What are the consequences of attaching an unused extra engine under Boeing 747 wing?
It turns out Boeing 747 can carry an extra engine under its left wing in case there's need to transport an engine somewhere far away. The engine is attached between the body and the left inner engine and isn't operational during such flight.
What implications does that have on the airplane operation? I guess drag is increased notably and also drag increases only for left wing and so the plane should tend to well, turn left in case engine thrust is equal on both sides of the plane so now engines under right wing have to produce more thrust or something like that. Also the engine weighs quite a lot so less cargo may be put into the plane. Also fuel consumption increases and flight range decreases accordingly.
Is that all? What are the consequences of attaching an extra engine under Boeing 747 wing?

You mean the left wing engines need to produce more thrust to offset drag, correct?  This would normally be done with rudder trim, rather than thrust, anyway.

No you've pretty much covered it.  There is likely a Flight Manual Supplement for spare engine transport that has performance charts for departure, climb, cruise etc with a penalty applied. There are obvious costs to doing this, but they are seen to be cheaper than shipping the engine on its own.

This is a perfect one for @Terry he may have even flown in this config before.

There may be some other implications like increased approach speeds, higher stall speeds, changes to emergency operations if one engine goes out on the left side, etc. Terry will probably know.

@JohnK it's the cost of extra fuel needed on a regular flight as compared to having to fly another aircraft on the route just to transport the engine. Yeah, it's going to be cheaper.

Operationally you would be more restricted in terms of trimming. Back when we had manual loadsheets there would be a demarcated area '5th pod operations limit'. Only the gods of the loadsheet deptartment would be allowed to do the loadsheet for these flights. I think Qantas would put a loadsheet man on board for these flights but I could be mistaken.
The flight would be re-timed as the usual 90 minute turnaround time would not be sufficient. I believe 2 hours on top of the regular turn was the norm.
An additional fuel stop was usually required as the fuel-burn was atrocious with that big thing hanging off. The weight penalty was compensated by reducing cargo.
I was working in Singapore in the 80s and we usually had Qantas doing this a few times a year. The engines were ex-SIN .. I don't know if they were overhauled in SIN or if they came into SIN on another freighter. At the time there were not many B747 freighters operating into Australia. I believe Flying Tigers had one but that was from US to Australia to SIN.. It did not do SIN-Australia.


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Can a prospective pilot be negated their certification because of too big/small hands?
Sorry if this seems a too naive question, I'm a complete newbie in this field. The question came into my mind when reading this answer from another thread (second picture).
There you see a photo of the throttle levers for a B747 with the pilot's hand on them. From that picture it seems that there is very little headroom for the pilot's fingers under the "heads" of the levers (unless the perspective of the photo is misleading). I can well imagine a pilot with bigger hands/fingers having some trouble handling the levers, especially in an emergency situation.
IIRC, to get a pilot's certification (at least in some situations) one's height must be within a prescribed range, but are there other less obvious "body size" requirements, such as hand size?
I assume that, especially for airliners, cockpits are designed as a "one size fits all" thing (please correct me if I'm wrong). Would this kind of problems also affects the chances that women (which statistically have smaller body size) can get a certification, despite their technical prowess?
I'm interested in any kind of regulations (civil/military, national/international) and also general facts about this issue (e.g. cases where pilot body size has caused problems).

Interest only. I have a friend who long ago  was the first in the world to ditch a (British Navy) Wasp helicopter in the sea. The manual said  to cinch straps tight for impact. The manual did not say that a slightly taller than average pilot could then not reach the throttle to stop the blades ricocheting off the sea and ultimately wrapping around the cabin. Presumably that was subsequently redressed. They both survived essentially unscathed. But wet

@RussellMcMahon Wow, that is scary! Plummeting into the sea and realizing you cannot control the thing because you followed procedures! I'm happy he survived! I can only imagine the amount of swearing against the designers (or the writers of the procedures).

it was even better than that :-). Ditching drill in a simulator copter and tank happened occasionally. It was disliked. Nobody had ever needed it. People avoided it. HE avoided it until they finally caught up with him - 1 week before the ditching. One of the requirements is to NOT undo your harness until the copter floods and inverts. He didn't. His companion unlatched early and was washed into the back and he had to rescue them. Better - he held the radio on transmit all the way down - usually a bad mistake. So they have his full commentary recorded - prayers and all. ...

... - it became the standard Royal Navy ditching training tape :-). Better -  they had flown out to a Cruiser? off Plymouth?, England and on the way back experienced very severe vibration. He called in an emergency and then tuned to land on a breakwater. Once facing sewared he found he could not read his instruments due to the extreme vibration. Fully dark and no instruments and ... .  Down they went :-) I don't know how high they were at that stage and preseumably he optimised what control he had.

@RussellMcMahon Whoa! That was a heck of an "adventure" for sure! Well eligible to be transposed into an Hollywood script, IMO. I hope all of the crew made it alive. If the helicopter you mentioned is this Westland Wasp that would have been before the nineties (according to Wikipedia that model was retired in 1988 by Royal Navy). No much help from sophisticated electronic localization equipment back then, I guess. GPS wasn't even fully operational at the time (and maybe not available outside US armed forces, not even for NATO military maybe).

Re Wasp retirement. In the late 1970s in a Baptist church here in NZ we had a number of theological college students. A number were adult students of various ages. One was this man. He had been a pilot in the RN before coming to NZ. I lost track of him. He was and a pastor and missionary in Africa. This page when he was 76! says "Born in UK 1936, Officer Royal Navy 1953 till 1967 when emigrated to New Zealand. High School teacher then church pastor. ... –
He'd be 86 now.

... Moved Australia 1995 and retired. Human rights work in S.E.Asia. Currently running charity for Zambian orphans, visiting them most years. Married 50 years. 3 girls and 5 granddaughters." Some retirement :-)

Having flown with pilots ranging from (American) football linebackers to rather petite individuals, I've never seen any issue with manual dexterity.  Hands and fingers are really amazing, and the controls in modern aircraft don't tend to be tiny, nor do they require particular strength to actuate.  There's probably some Human Factors work going into that, so that the widest possible range of pilots can manipulate them.
In college, there were discussions of tables that would show the 90% and 99% and 99.9% range of all sorts of dimensions, from fingers and hands to sitting height to pupil distance to probably everything else.  And designers can use that sort of information to make things so that they're accessible to the broadest possible audience.
Generally, the limitation is with height and reach -- can a pilot sit in the seat and have adequate reach to get the full range of motion on all the controls, and have adequate headroom?  That would be more of an issue with a particular aircraft, rather than a general pilot certification issue; just because you can't manipulate the controls adequately in "this" aircraft doesn't mean that you can't do so in other aircraft.
At the Air Force Academy, where some of the cadets are recruited for sports like football and basketball, the Air Force would fly a T-37 and a T-38 out to Peterson AFB so that those who wanted to go to pilot training could sit in the seat and be evaluated in the actual aircraft rather than a mock-up.  As I recall the story I heard (I'm not nearly tall enough that it was ever in doubt), if they could close the canopy without contacting the helmet, then the cadet was good to go to pilot training -- on that concern, at least.  I would expect that this may continue with the current trainers as well.

Interesting info, thanks (+1). Especially the issue of "reach" and the anecdote about the Air Force (I suppose you mean USAF) flying sportsmen around for "pre-testing".

Yes, the USAF.  And the "test" in the aircraft was just to put on the survival equipment (parachute and helmet, basically), sit in the aircraft, and close the canopy. No flying happened at that point. As I recall it (and this is a while ago, so things may be different now), this check came as cadets were preparing to choose their post-graduation assignments, ie during their senior year. Don't think prospective cadets being recruited had the same opportunity to know if they'd fit. Of course, between ages 18 and 22, height can change, so the check close to graduation would be what matters.

When I was active duty (a long time ago) the published standards were a minimum standing height of 5'4" and a max sitting height of 39". So someone in the 6' to 6'5" range might be disqualified based on body proportions. One issue that came up after women started flying is that there is a minimum weight for ejection seats. If you're too light, the higher acceleration could cause serious injury.

The US Army's airborne regiments had to start issuing different sizes of parachutes when they admitted women. The old standard parachute was made to be adequate for big guys with lots of gear. They found that if the smaller women used such a 'chute, and got into a thermal, they rose rather than descending.

@JohnDallman Wow, interesting info. I'd never have imagined the up vs. down problem, Thanks.

@Gerry thanks for the interesting bit of info!

The generally-used requirement is to accommodate the 5th percentile female to 95th percentile male. Mil-std-1472 is the parent document for most human factors work.

@fectin That's supposed to be for general applications but there's no guarantee, even for cars. I'm definitely within that range, and I've been in some trucks where I had the seat set to limits. It made sense when I got an automaker survey that asked what my height and weight was: they tailor them specifically for the expected driver population.


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What's the purpose of partial autopilot disengagement after applying certain force to the control wheel?
Aeroflot Flight 593 crashed after the autopilot was partially disabled by applying certain force to the control wheel but the only function which was disabled was controlling the ailerons. This partial disengagement went unnoticed for a number of reasons.
I'm reviewing the official accident report (text is in Russian, linked to from the Wikipedia article) and here're my findings from there so far.
The flight manual (cited in the report) is claimed to say that manipulating the control wheel to contradict the autopilot is definitely abnormal and should be avoided. The mechanism for overriding the autopilot is a safety device that engages outside normal operational conditions.
So it looks like there some functionality that allows to override the autopilot and partially disconnect it (so that only ailerons are no longer controlled) and it is claimed to be a safety measure.
What's the purpose of this functionality?

If an emergency maneuver is necessary you don't want the pilot to have to find the Off button of the auto pilot before he can do the necessary motions.

@ratchetfreak: Do the most likely emergency maneuvers need the ailerons only?

@sharptooth: I believe that if you push the column forward with enough force the old system would disengage autopilot pitch control. Basically the system previously allowed the pilot to disengage autopilot control of any individual aspect (pitch, roll, throttle) by using high force on the appropriate controls in the appropriate direction.

@ratchetfreak: That's the reason why autopilot should disconnect when pilot applies force to the control column. But does not explain why each axis disconnects independently. Note that A320 (that accident was A310) and newer don't have that mode any more.

Same as hitting the breaks on a car disengages the cruse control

The autopilot will disconnect on large control inputs because this is the most intuitive way to control the plane. On Boeing planes, the controls will physically move along with the autopilot. If the plane starts doing something you don't want it to do, the instinctive action is to grab the controls to correct it. While the autopilot button would normally be the way to disconnect the autopilot, it may not be the instinctive way in an emergency, and it can be helpful to already have both hands on the controls when the autopilot disconnects, rather than having one hand disconnecting the autopilot.
The reason for only disconnecting one part of the autopilot could be to help the pilot. Maybe there is a problem with the elevator controls, or an upset that affects the aircraft primarily in pitch. Maybe the TCAS gives a "climb" command. The pilot wants to take over pitch control to address this situation, but other controls are fine. While the pilot now has control of just pitch, the autopilot is still taking care of the other controls. The autopilot only gives the pilot control of the modes that are being overridden, instead of just turning off and requiring the pilot to deal with all control modes.

Although it doesn't address partial disengagement, this SB gives the reasons why forces on control columns could be used to disengage the autopilot.
Airbus Service Bulletin (sb) No. A300-22-6021 says

2) Objective/Action  To provide autopilot disengagement by applying a
  15 daN force on the  control column in go-around mode above 400 feet
  (radio altitude) this Service Bulletin recommends to modify the
  software at both flight control Computers.
The modified Flight Control Computers will also include improvements
  which have been identified from the last standard.
(3). Advantages
Operational benefit and/or passenger comfort by :

autopilot disengagement by 15 daN force on control column during    go-around above 400 feet (radio altitude),
avoidance of unwanted atopilot disengagement when the pilot    takes firmly the control column,
nose dowm improvement to avoid the pitch attitude increase after    main landing gear touch down,
improvement of "LEVEL CHANGE" mode; to avoid the "VMO" overshoot,
"ALT HOLD" mode improvement in heavy turbulence.
improvement of autopilot capacity to counteract strong vertical     gust in cruise.

n.b. 15 daN = 15 deca-Newtons = 150 Newtons = ~34 lbs.

The reason for this kind of functionality is that if you are handling the controls with that much force, the autopilot assumes you want to fly and gets out of the way.  The forces needed to do this typically are not the kind produced by incidental contact but rather from purposeful contact.  In the planes I'm familiar with the aural warning system will start announcing "AUTOPILOT" until you hit a button to silence it.  In addition, the autopilot annunciation area will indicate the change in autopilot mode or disconnect.  These indications should be monitored at all times the autopilot is flying and the chain of errors here is:

inadvertent autopilot disconnection (partial), and
failure to properly monitor the airplane.

Bringing your children onto the flight deck and encouraging them to play with the controls in-flight.


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What's the name and purpose of a barrier raised behind a carrier based jet?
I saw this picture in Wikipedia with a Su-33 jet on carrier deck with some barrier raised from the deck behind the jet tail:

What is this barrier for and what's the official term for it?

It's a jet blast deflector. See also http://aviation.stackexchange.com/questions/6336/what-are-the-steep-ramps-often-erected-at-large-airports.

The official name is a Jet Blast Deflector.
As the name suggests, they direct the fast-moving and hot air from the jet engines upwards. This protects the personnel and equipment behind the departing aircraft from getting blown around or damaged from the jet blast. Because of the high temperature of the jet blast, they may have active cooling systems, and must be allowed to cool sufficiently before being used as regular deck again.
To illustrate the risks, see this video, which shows a vehicle being blown away by a 747.
There was also a recent event in Pakistan where a 737 damaged the tarmac (and, as a result, itself) during an engine run-up.
To make a comparison, each engine on a 737-400 can produce up to 22,000 lbf (98 kN) of thrust. The Su-33 in your picture has two engines close together which can each produce 16,750 lbf (74.5 kN) of thrust, or 28,214 lbf (125.5 kN) with afterburner.  That's a total of 56,248 lbf of thrust in afterburner, or 2.5 times the force of one engine on the 737-400. Of course, this does not directly equate to jet blast or temperatures, but it is a good indicator of the forces involved.
To provide a better idea of the jet blast, see this chart (based on the 737-800). At 20 m behind the tail (which is about 20 m behind the engines), the jet blast can reach 300 km/hr at takeoff thrust. For more details about jet blast on the 737 series, see the Boeing documentation.
The CFM56-3 (used on the 737-400) can produce exhaust gas temperature (EGT) of up to 930 C at takeoff. This will mix with the cooler bypass air (and ambient air) to reach cooler temperatures further behind the engine. Military jet engines have a smaller bypass ratio, which means there is less of the cool bypass air in the exhaust to mix with the hot core exhaust.

The 737-800 chart makes no sense. First, the axes are the wrong way around -- you choose the distance behind the tail and measure the exhaust velocity there, so the distance should be on the horizontal axis and velocity on the vertical. Second, the small secondary peak at velocity ~230 means that the graph claims three different velocities at ~30m aft (about 180, 220 and 240). Third, a 737 at take-off thrust really generates 60kph winds half a kilometer behind itself? That seems infeasibly high, given the turbulent flow.

@DavidRicherby I agree that the axes should be switched. The peak around 230m is due to the function chosen to connect the data points. However, the values do seem to match the Boeing data. The velocities do seem high, but this is why they have blast fences. Just watch that linked video: those engines are 3 times as powerful as a 737 engine, but still have high velocity blast at least 100m behind the engines.

Those Lyulka 31 engines have a much lower bypass ratio, hence a much higher exhaust speed, than any of the 737 engines you mention. OTOH, the mass flow is lower, so the jet blast is smaller in diameter but more intense.

Remember also that catapult launched aircraft go to full afterburner just before the launch - the blast from a military engine at full afterburner is not inconsequential.

It's a blast fence to prevent that the groundcrew walking behind the jet get blown away by the jet blast.

It is a blast fence to protect the planes behind it from the destructive force of the jet blast of the plane in front of the fence.  The plane in position for takoff will go to full power for takeoff.
Check out this video of a pickup truck being towed through the full power exhaust behind a jet.  https://www.youtube.com/watch?v=DFP4xl0V0mk

The Top Gear version is more fun. :-)


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What is the name for the Mitsubishi A6M Zero's one-piece wing/fuselage?
The Wikipedia article on Mitsubishi A6M Zero fighter cites an article from Life magazine published on Nov 4, 1942:

The Zero's fuselage and wings were constructed in one piece, unlike the American method that built them separately and joined the two parts together. The Japanese method was much slower, but resulted in a very strong structure and improved close maneuverability.— Wikipedia

(Source)
This design is harder to implement but it allows for higher strengths for the same weight or lighter weight for the same required strength.
Is there a name for such fuselage design?

The construction of the Zero was slightly different from that of its western counterparts. The aircraft had three major sub-assemblies:

wing/center fuselage
forward fuselage, and
aft fuselage.

The construction of the first sub-assembly was such that the both the wings were constructed as one piece integral with the cockpit. This is (presumably) what the author means in the article in question. Otherwise the wing was a semi-monocoque structure with two main spars, which is quite common.
The image below shows the sub-assembly in question (the wing+cockpit section) from a recovered zero. It can be seen that there is no great difference in design, only in the choice of the sub-assembly (a wing+cockpit section, instead of wing + fuselage).

A6M Zero midsection; image from lasamurai.blogspot.in
The images below show the different sections of the aircraft (middle and rear sections) from a rebuilt Zero.

Cockpit+wing sub-assembly; image from j-aircraft.com

Rear fuselage assembly; image from j-aircraft.com
I'm not aware of any special name for this. It appears to be a normal semi-monocoque structure.


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Where do all the bullets end up?
When planes engage with guns, many of the shots are misses... what happens to the bullets? Do they kill people on the ground and damage facilities? Do we have any records of this happening?

Do you mean air-to-air or air-to-ground?

Either way, although in the air to ground situation, damaging people and facilities on the ground is probably the intent, rather than a problem

Do they kill people on the ground?

Almost certainly a few do.
People struck by falling bullets are more likely to die than people shot directly. The chances of a particular bullet falling onto a person are very small but over the decades, many many bullets have been fired by aircraft.
Handgun bullets

Between the years 1985 and 1992, doctors at the King/Drew Medical Center in Los Angeles, California, treated some 118 people for random falling-bullet injuries. Thirty-eight of them died.
Bullets fired into the air during celebrations return at a speed fast enough to penetrate the skin and cause internal damage to other organs in the path of the migrating bullet. The bullet’s velocity required for skin penetration is between 148 and 197 feet per second. A velocity of less than 200 feet per second, which is easily obtained by a celebratory gunfire, is capable of fracturing bone and even causing intracranial penetration [4]. Spent bullets have the capability of reaching up to 600 feet per second during their downfall, and thus they have the ability to inflict damage to multiple body cavities [4]. The larger caliber bullets (ie, .45-caliber) reach a higher terminal velocity compared with the smaller caliber bullets (ie, .30-caliber), because of the proportion of their weight to their diameter [4].

From http://www.annalsthoracicsurgery.org/article/S0003-4975(06)00831-9/abstract

For those hit by falling bullets, the chance of the wound being fatal was far higher than a typical shooting. The hospital put deaths from regular shootings between 2% and 6%, while for those struck by falling bullets the death rate was close to one third.

From http://www.theguardian.com/world/2011/aug/24/how-dangerous-is-celebratory-gunfire

Aircraft rounds
These falling bullets were from celebratory gunfire, not fired from aircraft.
Aircraft cannon fire projectiles which are often much heavier than handgun rounds. If one falls on you, the likelihood of injury or death must be higher.

.22 Winchester magnum rimfire and .50 Browning MG rounds at same scale. source

Falling bullets are similar to falling stones, albeit with higher density and higher terminal velocity. Small ones won't do much damage, but I don't want to be hit by one from a 37mm cannon. Same goes for shrapnel: Flak/AA-guns could not fire steeper than approx. 85° to prevent the gun crews to be hit by their own shrapnel.
One airplane became famous (at least in pilot's folklore) for the ability to shoot itself down. According to that rumor, the Republic F-105 could outrun its own bullets in a shallow dive at supersonic speed. When the bullets, having been fired in horizontal flight, slowed down due to aerodynamic friction and went down in the usual parabola, an accelerating, diving plane could catch up with the bullets. The relative speed between both would be small, however, so the kinetic energy would cause less damage than bullets straight from a gun.

This is documented to have happened to an F11F-1 while being tested, he shot himself down.

@GdD: Mentioned here: http://en.wikipedia.org/wiki/Grumman_F-11_Tiger#Design_and_development

You are not the first person to worry about this.  In the 1942 war movie Mrs. Miniver a principal character is killed by stray bullets from an aerial dogfight.  This was considered quite realistic as rounds fired in a low-altitude dogfight often had plenty of kinetic energy when they hit the ground.


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Why do (almost) all military transports have high wings and civilian transports low wings?
I've observed that almost all military transports have high wings (with a pronounced anhedral) and almost all civilian airliners have low wings (with a pronounced dihedral) — why is this?
The high-wing configuration gives the military the advantage of easier loading and unloading (especially when operating from irregular airfields), and lower overall height for the aircraft, but then why do civilian aeroplanes hate this design?
Except in the erstwhile USSR, I haven't really seen high-winged military aircraft being used as civilian airliners (Boeing 737 size and beyond), though I can't think of any reasons why not.

possible duplicate of Pros and cons of high-wing vs. low-wing design

For military transport aircraft:

Wings further off the ground will mean that the engines will also be further off the ground, reducing the risk of foreign object damage.
You can move vehicles under the wing, and taxi across smaller taxiways.
The fuselage can be closer to ground, facilitating transport.
No wing spar crossing the cargo floor.

Reasons why most commercial transport jets don't have it:

Many are converted passenger jets.
They are mainly pallet loaded, less vehicles and bulky objects.
They normally use prepared airports, which military jets cannot assume they will.
They often loaded from a side door, and it makes little difference I think if you go up one meter or three meters.

but then why do civilian aeroplanes hate this design?

Airlines don't 'hate' this design, look at the BAe146 Quiet Trader for instance. It's just not that many commercial aircraft from which cargo jets are derived are built this way.

Except in the erstwhile USSR, I haven't really seen high-winged military aircraft being used as civilian airliners (Boeing 737 size and beyond), though I can't think of any reasons why not.

Military jets are very expensive to operate and the east block Antonov 124 probably satisfy the most demand. There are a few commercial C130 (L100) around though. It's also not like the US airforce will give us C-5 Galaxy to a commercial company to do whatever it wants with it.

US airforce won't give C-5 Galaxy to a commercial company, but Lockheed would happily build and sell them L-500 if they wanted. None did.

AFAIK, the primary reason military transports are so expensive is because their volumes are so low. Volumes are low because only militaries buy them. Catch-22.

Was just reading Sutter's book on the genesis of the 747. He reports that the C5 was considered as the first jumbo airliner. However, the design, being optimized for military use, was just too fuel hungry for efficient commercial use.

There are probably two main factors that come into play with the placement of the wing:
Height of fuselage from ground
Especially for military airlifts, the ability to load cargo is extremely important. They need to be able to load large objects and vehicles, and with little or no ground support available. This means that the fuselage should be as close to the ground as possible to allow roll-on/roll-off of cargo with built-in ramps. Placing the wings on top of the fuselage allows the bottom of the fuselage to be closer to the ground.
This is less of a problem for airlines. Commercial cargo can usually count on ground equipment for loading and unloading cargo containers on aircraft.
Ease of maintenance
Since airliners don't need easy access to the fuselage to load cargo, maintenance should be as simple as possible. Especialy with the larger aircraft like the C-5, a high-wing puts the engines and wings far above the ground. This makes it much more difficult to work on these components. Keeping the wings and engines low to the ground makes it much easier to replace an engine or access the wings, such as for refueling.
The military wants planes to be easy to maintain as well, but they are willing to make some tradeoffs for the better cargo loading configuration.
There are of course many other tradeoffs in areas like structure and stability. However, it's clear that both configurations are perfectly feasible. The most important factors come down to the usability of the design.

Low wings are favored for civil aviation because this puts the passenger cabin on top of the wing. Damage from non-normal landings (gear up, no runway, missed the runway, etc.) will happen to the wing, first. Thus protecting passengers. Fuel tanks are usually in the wing and having them also underneath is considered good for the same reason. A low wing allows engines to be near the ground for easy servicing. And main gear legs fit conveniently into low-wing structures. The legs are tidy and short with low wings.
High wings are favored for military cargo and passenger planes because the high wing keeps the engine, propeller, fan, etc, away from the ground. Military cargo and passenger planes don't always have paved runways- a flatish spot may be as good as they get. High wings make landing gear design more difficult, they're either taller, or stick out from the fuselage and are narrow, maybe mounted in pods on the sides of the fuselage, with extra weight and drag. High wings require strong structure to keep them from crushing the passenger space, in a crash, which is extra weight and complexity. High wings make fuel tank access and engine access difficult. But high wings protect the engines, and that allows high wing airplanes to operate in rough conditions. Meaning it can take off again, after each landing.
Dihedral provides stability to low wing airplanes by giving negative feedback to stabilize straight and level flight. Anhedral reduces stability, allowing a high winged airplane to be maneuvered more easily, but doesn't enhance straight and level stability.

Why not give military (transport) planes low wings with engines mounted on top of the wing (like in the Honda business jet)? This would seem to combine the benefits of both...

@markvgti it's been tried to build such. See the VFW614 for example which was a civilian regional jetliner intended for export to places with unpaved runways. It failed for lack of orders. Problem is the engines become hard to reach for maintenance purposes (same reason trijets are disliked by maintenance crews). And there's still the risk of stones and stuff being kicked up by the landing gear damaging the undersides of the wings.

How is having the fuel tanks closer to the ground, where they're much more likely to be damaged in a crash, considered good?


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Why use an airplane with non-retractable landing gear for aerobatics?
I'm watching footage from Red Bull Air Race 2017 in Kazan (one example is

) and clearly at least some of the airplanes used have non-retractable landing gear.
I was under impression that non-retractable landing gear increases drag and also makes the airplane larger which is hardly good for application where maneuverability and speed are important.
Why are planes with non-retractable landing gear used in such competitions?

anyway the video is accelerated, just to seem more impressive.

Weight, plus 6+ G's on the gear may cause them to extend.

Related: Why do most aerobatic aircraft have conventional landing gear?

Your title says aerobatics but the question references a race series.  They are not the same thing.  Many of the considerations in the answers apply to both, but it is not obvious that the same answer is right in both cases.

I think the course design in the Red Bull Air Race makes turns (i.e. acceleration) more of a limit than outright speed. Compare with the Reno Air Race.

As you mentioned, drag is one of the reasons why retractable landing gears are used in the first place. But in order to use it, there are way more considerations than just drag.

Scale: Size of the aircraft plays a big role here. Big aircraft have more room to keep the retracted landing gear. This is an issue as planes get smaller.
Weight: Retractable landing gears not only require more space, but they impose more weight
Cost: They add extra costs in installation and maintenance.
Application: High speed applications justify a retractable landing gear for a more aerodynamic shape. Does the present situation really need the application of a retractable landing gear?

These are some considerations that go into it, but not all of it. In the case of a high performance sports plane (like in the video above):

Scale: the planes are small. The retractable landing gear systems (system) need a lot of space. This is not what we want in a sports plane
Weight: A high percentage of the overall weight is taken by the system. This in turn increases the inertial forces* and decreases the overall maneuverability.
Cost: It is expensive to install. And it may cost even more due to the low volume requirements.
Application: More than high speed, high maneuverability is needed.

* Inertia is the tendency of a body to stay in the existing state of rest or motion. So inertial force is the force that keeps the body in its existing state of rest or motion.
[EDIT]
Based on a very good response below (from @Devil07), I am adding this important point here (just for a better overview of all important aspects):

Complexity: Retractable landing gears are complex piston mechanisms. Eventually it adds to the cost of installation and maintenance of the system.

Also short flights mean the fuel savings from retracting the gear would be minimal, especially combined with low speeds.

@MichaelKjörling. I will keep your suggestion in mind for the next time. Thanks for your input.

I'd argue that installation and low-volume manufacturing costs would be pretty low on the list for the top performers. Zlin Z-50 (about 80 were built between 1975 and 1994) uses fixed single-piece titanium spring, which was veery expensive to manufacture.

To add to point 5, complexity would also add a point of failure to emergency landings. At low altitudes the time to deploy landing gear may be to great.

+1 for definition of intertia, first time in many years and after many arguments and debates, someone has admitted that the tendency to stay in the initial state of rest is also described as inertia.

Strictly speaking, a 'pure' aerobatic  aircraft doesn't need a retractable landing gear. For such an aircraft maneuverability is much more important than speed. In fact, the aircraft can't fly too fast or the spectators are going to miss the show.
In case of air races, the weight penalty of having a retractable landing gear is huge- in addition to the problems associated with complexity. For example, all the aircraft used in the Red Bull air races are lightweight with carbon fiber wings. As Popular Science notes,

Extreme weight reduction techniques are employed to give pilots even a minor advantage, such as discarding plastic tie wraps in favor of lightweight string, or drilling holes in heavy brackets

Trying to fit a retractable landing gear inside would incur a weight penalty too large to negate the drag reduced especially since the propulsion system (engine + propeller) is fixed. In this case, the drag is reduced by putting the landing gear inside aerodynamic covers. Not to mention, larger wings reduce maneuverability.
Note: In case of Red Bull air races, it appears that the fixed landing gears are mandatory:

The following key rules and regulations were taken from the Red Bull Air  Race World Championship Regulations 2010 Edition ... Regulation  6.4  states  that each aircraft must have fixed landing  gear  on  board.

May be worth noting the weight wouldn't increase by the weight of the landing gear alone. Increasing the weight of the landing gear system would mean the entire airframe would be under a heavier load in every manoeuvre (f=ma), and, assuming they are built to the limit of performance, every load bearing part of the aircraft would need to be strengthened, increasing the total weight further.  (and increasing the total weight means you need stronger, heavier landing gear to withstand the landing forces!)

In the case of the Red Bull Air Race, the engine and propeller are specified by the race officials, and must remain unmodified, so the airframes are designed to get the most out of that combination. The (relatively) tight layout of the course benefits a highly aerobatic aircraft of the Extra 300 style. Fixed gear is also required.
As a result of those requirements, the cost of both purchasing and maintaining the competition aircraft in the Red Bull series is relatively low, meaning more competitors and more races.
While the Red Bull series (which I really enjoy) holds numerous races in multiple locations each year, the faster and infinitely more expensive aircraft in the Unlimited Warbird Racing Class race once a year at Reno, NV.

Less weight: (as others have stated)
Less complexity: which translates to higher reliability
Robustness: retractible landing gear on small aircraft tends to be a bit flimsy (and if it isn't flimsy then it adds to the weight penalty), imagine pushing and pulling on all those moving parts with 6gs of force back and forth and back and forth. Fixed landing gear is less likely to fail, especially under those repetitive forces on all the moving parts.
And finally, as mentioned, most aerobatics are done as slower speeds where the penalty of fixed landing gear is not much of an issue. Slower speeds = tighter turns and maneuvers.

Retractible landing gear on small aircraft is flimsy, have you got a source for that? If most items are mentioned before, what does thiss answer add?

Personal experience. It adds brevity/conciseness. Feel free to vote it down if you disagree. I appreciate lots of answers when I ask questions, so I'm just contributing the best I can.

@Koyovis if a small aircraft is not designed and certified to be aerobatic, there is no point designing landing gear (ether fixed or retractable) which will handle high G loads, flying inverted (including the effect on hydraulic systems, not just the moving mechanical parts), etc. For aerobatics, you have to consider all of those options - plus either designing the gear so it can be extended/retracted while flying inverted, or in the middle of a +6G or -6G turn (because some aerobatic pilot is going to want try that just because it looks "kool"!), or adding some interlocks to prevent it!

@alephzero Yes a retractable landing gear on an aerobatics machine must be designed for 6g and therefore becomes not flimsy, but robust and heavy. Weight, as others have stated. This answer adds nothing to aeroalias' answer.

Also, slower aircraft means more time over the crowds at air shows. Not much point in aerobatics at 300+KIAS, they'll be out of sight of the crowd that pays for the event very quickly.

Safety
Engine Failure @ Low Altitude Followed by Gear Malfunction
Aerobatics and racing are performed at low altitudes.  If you lose the engine at 500 ft AGL, and the gear are stuck (due to your aerobatic maneuvers) or you have an electrical or hydraulic issue, what are you going to do?  Hand crank the gear down in an plane with really high wing-loading (meaning higher rate of descent at best glide)?  You won't have time and you'll be belly-landing.
Engine Failure @ Low Altitude above VLE/VLO
Additionally, lets suppose you are racing at low altitude, and going fast because that's the point of racing... you lose the engine, which will slow you down, but not necessarily enough to get below VLE/VLO.  What do you do?  Pull some crazy maneuver at low altitude to bleed airspeed?  Wait it out and hope you slow down enough and still have enough time to drop the gear?  Drop them anyways and risk damaging the gear, or worse, the air frame, all while getting buffeted like crazy due to the huge and sudden drag and while trying to perform an emergency landing?  No thanks.  Fixed gear pls.

This looks like the most practical answer however it's rather hard to read it because it's formatted as a single large block. Could you please split it with newlines?

If you lose an engine at low altitude and high speed, why not pull up and convert that speed to altitude?

Well, drag slows the speed down which is good for a spectator sport.  It also gives the plane visual legs which give turns and spirals optical anchor: this makes them look more like acrobatics than swimming.  If you use sleek jet planes for aerobatics, stuff becomes quite faster and more dangerous (both to pilots and spectators) with much larger turns while looking actually more bland.


text:
What kind of identification code is this format? (AAA0000)
From what I understand, an aircraft's registration number is its ICAO code in the pattern found here: Wikipedia: Aircraft registration, but I have seen references to aircraft using a 3-letter code (I'm assuming it's an airline code) followed by a 4-digit number. (Example: PAK0032) What kind of a number could that be?

Could you specify where you have seen such references? It might help identify what they are.

It's in a database my company has where airlines can enter their aircraft's information. Generally this ends up being the tail number, but occasionally it isn't, as in this case.

That format is the flight id. The first three characters are the ICAO operator code which identifies the airline. The rest of the characters are unique to that flight. The first character after the ICAO operator code is always a number, after that both numbers and letters are allowed. The maximum length of the flight id is 7 characters.
The flight id is transmitted to Mode S radars by the transponder and also broadcast on ADS-B. It is used to correlate a flight to a flightplan.
The flight id is also the basis for the callsign used in radio communications. The ICAO three letter code represents the airline's callsign, the rest of the code is pronounced in the ICAO alphabet.

The registration for an aircraft follows the nation's letter assigned by ICAO, correct.
But this is not the only instance where ICAO is used. When the registration is not used as the radio callsign for the aircraft, They will use the flight number to address the aircraft on the radio.
The flight callsigns do not always follow the flight number you see on your ticket, especially since the radio callsign uses the ICAO code for the airline instead the IATA code on your ticket. Some airlines even replace parts of the flight number, either to avoid similar callsign at the samw time or to obfusticate which flight it is.

LH4892 could be known to ATC as DLH48RA

Some transponders can be programmed to broadcast the flight number if they operate with ADS-B. In these cases they carry a specific hexadecimal value, which can look similar to the code you posted, but can have the hexadecimal values in any place and not only the letters in front.


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Axis of rotation of tail surfaces
In cases where complete tail surface rotates (be it horizontal, vertical or at angle) what should be preferable axis of rotation of surface.

We don't need all these votes for closing a perfectly valid question of a new contributor.

@Koyovis The question is flagged as unclear what you're asking and it is indeed unclear to me what exactly the OP wants to know. If you understand, could you edit to clarify?

@Bianfable Why would we close the question though, and not simply ask for more info in a comment.

A legitimate question. While there is some engineering design discretion, there are practical limits to where along the chord line of the control surface the pivot point can be located. I'm voting to leave open.

@Bianfable It looks clear to me. Is there a particular thing about it you find unclear?

Picture source
The axis of rotation of the F-16 stabilator can be seen on the picture. Design should be such that:

The airflow attempts to bring the surface back to neutral from a deflection. Meaning: more surface aft of the hinge than before the hinge.
The aerodynamic resistance moment is relatively constant, and of not too large of a magnitude. This can be achieved by choosing the hinge near a point where aerodynamic hinge moment is relatively constant, as function of angle of attack.

The most suitable axis of rotation would be the aerodynamic centreline, around 0.25 chord for:

Symmetrical airfoils.
Subsonic flow.
Limited range of deflection.
Zero sweepback angle.

For supersonic flow, the Centre of Pressure shifts aft and the aerodynamic centre of the surface is about 0.5 chord. For sweptback surfaces, there is relatively more area aft of the hinge line and the hinge should move aft.

Thanks. Under what conditions we can/have to differ from this preferred choice.

A "preferable" solution depends on many factors, both in aerodynamics and in design/construction. There is no single best solution for all situations.
On slow(er) subsonic aircraft with reversible control, the main concern is to provide convenient force on the yoke/stick. For symmetric airfoils, which are common for tails, there is a point at 0.25 chord where the hinge moment will be zero for all the operational range of deflections. To provide some positive force, you'll want to put the axis slightly ahead of this point.
However, there is another problem: stability with relaxed controls. If you move the axis too much forward, making the surface 'weathervane' with the stream, you reduce the control-free stability. This is an important consideration because when you are flying 'hands off' on a well-trimmed airplane, this is exactly the situation you are in. With classic hinged elevators, this effect is already quite noticeable, but with all-moving tails, it can be extreme, up to the total loss of stability. On the other hand, obviously, if you put the axis aft of this 25% chord, you'll have an outright unstable configuration.
So the ideal situation for such airplanes is to have the axis at 25% chord, but to create positive control force with springs or with an anti-servo tab, like on PA-28:
$\hskip 6cm$
Source
For supersonic aircraft, the situation is somewhat different.
First, their control is typically irreversible: the actuators take all the load. This means that the control-free stability problem doesn't exist; and the actuators can potentially control high (or even negative) hinge moments.
Still, you don't want to oversize the actuators unnecessarily. In addition, many (older) supersonic aircraft allowed for fully manual or assisted control in case of hydraulics failure, so the aircraft still had to be flyable by hand.
This again puts the best hinge location near the 25% chord point.
However, the second difference is the fact that at supersonic speeds, this magic 25% chord point (called aerodynamic centre) moves to 50%. On top of that, the relative efficiency of control (per degree of deflection) reduces, and this is actually one of the main reasons of using all-moving surfaces on supersonic aircraft. This, obviously, creates enormous hinge moments.
To reduce them, we could move the axis a bit back. This may create negative moment at subsonic speeds, but if we have a full-authority hydraulic control, this may be the optimal solution. Some 4th-generation fighters seem to follow it.
The third difference is that supersonic tails are often highly swept back. How do you align the axis then?
$\hskip 1cm$
Again, there is no best solution for all cases. Aerodynamically and kinematically, the straight axis (on the left) is a bit better: it creates direct linear control. Structurally, it depends on how the stabiliser and the tail section are designed.
If there is a possibility to use a common shaft for both halves of the horizontal tail (which is typically true for T- and cruciform tails), this is a enormous advantage and it naturally leads to the straight axis. On the other hand, it is usually easier to integrate the shaft (or hinge points) along the spar of the stabiliser, which favours the swept axis for most swept tails.

Your statement on reversible all-moving tail is correct. However, it's not a matter of where to place the hinge (assuming ahead of 1/4 chord). Rather, without an anti-servo tab, the stick-free neutral point moves to the wing AC! The tail might as well not be there. An anti-servo tab helps, somewhat, but now your HM is even worse. I think a reversible all moving tail is just not realizable.

What do you mean 'not realizable'? What about PA-28? Now theoretically, it only matters whether the axis is ahead or behind the tail AC, yes, but in practice, given the friction and inertia, there is some margin, so the AC (25% MAC) remains a practical optimal hinge location. (Still, I'll add a clarification).

Interesting. I don't think an anti-servi tab can restore the stick-free NP by much more than 10%. Does that mean it has a large trim drag while designing for field performance?

I don't know; PA-28 feels quite stable. But why should it be large? In my understanding, the only way a reversible trimmable all-flying tail can work is to have the axis slightly ahead of AC. This makes aerodynamic trim work; and the stick-free stability must be provided by anti-servo. The 'weatherwaning' hinge moment per AoA of the tailplane itself is easily measured/calculated, and we can kinematically link the anti-servo to provide an exact same counter-moment, thereby fully restoring stick-free stability.

Yes. But this is rarely significant for the tail. On the other hand, your effective deflection will be moderated by cos(axis_sweep), which can be very substantial.

I derived a simple model of anti-servo tab and the effect on NP assuming a stick-free stab. Without the tab, the NP goes straight to wingbody AC. If you gear the tab to stab 1:1, I gain back max 10%. Gear to 1:2, I get max 15%. Maybe a gearing of 1:2 isn't too bad for full-chord controls? My line of thinking was that if the stick-free stability is low, the CG would need to be further forward, resulting in larger trim drag.

How did you account for the relative chord and location of the anti-servo tab? Gearing alone is not sufficient. Generally you don't even need to involve the wing here. Assuming symmetric tail airfoil, its hinge moment derivative per AoA will be $h \cdot L_{\alpha}$, where all terms relate to the tailplane itself, and $h$ is the distance between the axis and AC. Now, given that $h_{servo}$ is much (~10x) longer, nothing prevents us from compensating the hinge moment (fully or partially) with any reasonable combimation of gearing and servo size. This is how any trim tab works.

I think you are confusing hinge moment balancing with stability. Trim tab can balance the HM so that you get a trim point; but it does not restore the stick-free stability to stick-fixed. The longer moment arm from the tab is instrumental in HM, but does very little for stability (manifests as a change in tail Cm, which is generally ignored).

Well, theoretically it can. If you just put a hinge exactly on AC, without any trim/servo (and assuming symmetric airfoil to avoid static moment), then nothing will make the relaxed tail turn, and the situation will be equivalent to stick-fixed stability, if we started off a stable condition. With a servo, you can recreate a similar situation for other axis locations.

Since you need to meet the stick force/V and stick force/G requirement, you cannot put it at the tail AC (that's a theoretical point anyway). Once you have an offset, the static stability reduces to stick-free. Again, the anti-servo helps, but only so much. We can take a look at the maths, but I don't think my assumptions are egregious that led to my former conclusion. If you have some maths/references to back yours up, I'd be happy to take a look.

Let us continue this discussion in chat.

This answer only addresses one particular facet of the question.
If we rotate a pair of surfaces (like horizontal stabilizers) around swept hingelines, we create an anhedral or dihedral geometry  as we raise or lower the trailing edges of the surfaces, respectively.
This is a result of simple geometry, not obscure aerodynamics-- if this is unclear, consider sweep angles approaching 90 degrees.
In the case of all-moving horizontal stabilizers, this would tend to lead to a variation in the aircraft's overall amount of "effective dihedral" based on the fore-and-aft position of the control stick. This would generally be considered a disadvantage of this particular configuration.
By the way, the general principle we're noting here is true even for surfaces like flaps or speed brakes-- any matched pair of moving surfaces-- but lowering flaps or deploying speed brakes probably changes an aircraft's flight characteristics in so many ways that the swept hingeline's contribution to a decrease or increase in "effective dihedral" is not particularly  objectionable.


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Why do jet nozzles close at different rates?
After recently seeing the trailer for Top Gun 2, I was reminded of something that I always wondered about: why do the nozzles of some jet aircraft seem to close at different rates?
Sure, it's likely that both engines of the aircraft won't spool up at the same rates, but what about the nozzles? Are the nozzles dependent on the engine power output (which would then answer this question), or are they independently controlled? If so, what causes them to close/open at different rates?
Here's an example from the Top Gun 2 trailer:

The nozzle position is automatically adjusted according to the current engine state to maintain optimal exit flow conditions at the end of the nozzle.
The difference in nozzle actuation you are referring to is caused by a slight difference in activation time of the afterburner between the engines.
Please see the following Aviation Stack Exchange question and answer(s) for more information on the purpose of the nozzle:
Why are adjustable area jet engine nozzles mostly limited to military use?

This photo show as the afterburner (left one )  literally just got ignite first  one . So it is clearly to me the nozzles diameter is different ,one from another , (just for seconds)to ensure that the pressure of the gases exhaust  is  able to provide thrust. The left nozzle is opened more  because the more mass of the burnt fuel left jet engine provide.To answer your question, the  nozzles are not closed/open by the  pilot lever or switch ,only the power setting thrust  (for saving the fuel or lower the temperature in one )witch could be seen as difference in exhaust nozzles system )But sometimes , if engine is not running good the specific emergency settings will be able to do fixed pre-sett diameter to ensure the proper thrust for safety. reasons.https://theaviationist.com/2019/12/26/tu-22m3-backfire-engines-transition-from-idle-to-full-reheat-captured-in-stunning-detail/?fbclid=IwAR00KfC3zHPVln6wXGT6_5fyT7uWQGTta7RGe_3KwsDNemDZP21prTSen70